Plate wall girder



Sept. 15, 1931.

H. WAGNER PLATE WALL GIRDER Filed June 29, 1927 2 Sheets-Sheet 1 Sept; 15, 1931. I i H. WAGNER L 19 PLATBWALL GIRDEVR Filed June 29. 1927 2 Sheets-Sheet 2 Patented Sept. 15.1931

UNITED STATES PATENT OFFICE nnnnnnr WAGNER, or BERLIN, Grimm, assrenon '10 mm! mm nonnnacn uEuLL-nueznuenau e. 1;. B. n., or BERLIN, exam 2mm wan. emnna Application fled Iune'29,'1987, 8erla1 No. 202,422, and in Germany July 9, 1928-.-

5 the small air forces arising'in flying service require bodies of ample dimensions, such'as, for instance, fuselage, wings or the like. The marked extension of the structural parts combined with the comparatively small effect of the acting forces per unit of area result in bars and plates of thin walls and of small bending strength against shearing or compressive stresses, thus offering considerable inconveniences of construction.

It has heretofore been particularly diflicult to eliminate such bending sym toms in the outer skin, coverings of large sur ace area, which are called upon to transmit transverse forces occasioned by bending and torsion J stresses; The prevailing practice was to impart suflicient shearing strength to the cover skin by either using corrugated sheet iron .for its structure or by suitably re-inforcing it by means of some special supporting system. The corrugating practice oflers inconveniences from an acre-dynamical point of view, whilst the latter causes an increase in weight. With hollow bodies has been proposed to use, for the transmission of transverse forces, in addition to the cover plating, intersecting tension ties running from junction to junction, or,'instead of the latter, diagonally arranged reinforcing members. With this structure the skin substantially serves as cover only.

The present invention, however, produces more favorable conditions with regard to the transmission of forces and utilization of building material. It can, in a certain sense, be compared with a bending girder, which consists of upper and lower girders and a transverse force-transmitting part formed of vertical plating and transverse reinforcing bars. According to the present invention and in contradistinction tothe usual type of plate stressed against shearing, the vertical plate is provided with such thin walls, that it forms a closed diagonal panel with transverse folds, when stressed by transverse 50 forces.

With approximately 1/5 of the breakin load applied the folds, recognizable even wit the considerably smaller load'of 1/20 of the breaking load, are distinctly pronounced. When the stress acting is not reater than 2/3 ofthe breaking load, the olds vanish when the load is removed. The stress occurring under normal service conditions, will besomewhat near 1/4 of the breaking strength. The resulting folds have no influence on air flow conditions.

The line of the folds, which is not influenced by diagonal reinforcing members andtheir relative distance from each other, is inclined towards the girders by to These folds caused by compression strain and uniformly extendmgover the whole panel, are a distinct and unmistakable characteristic of the stressed vertical plate according to this invention. I L

The invention renders it possibleto'utilize, instead of the above indicated intersecting tension ties provided for both stress-directions, substantially the whole cover skin for the transmission of transverse forces. The structure of the plate-wall girder is-simplified by the elimination of the diagonal members (cross members and reenforcing members) and their junctions. When compared with the shearing-stress resisting plates structures-of the prior practice the present invention has a very substantial advantage owing to the thin walls. The tension plate further has a favorable effect on the girders, the thin flanges of which are particularly well protected against bumping, which means, that greater forces 'can be transmitted than with the tension plate missmg.

With regard to thebendingmoments caused in the girders by the new construction it is desirable to arrange the push bars or force transmitting members at rather close intervals, in order to reduce these bending m0- ments. Through thetension effect of the plate the compression members are substantially secured against bending not only inthe plane of their connection with the in the vertical direction.

In normal practice the approximateplate, but also lyequally long cross members are, according to prevailing circumstances, arranged at intervals of approximately 1/8 to 1/12 of the plate girder height. This means that one diagonal fold is crossed several .times by cross bars. It is of course possible. to an range the cross members at various intervals, according to special circumstances.

The invention is of special advantage when applied to girders stressed in the direction of the cross members by'forces from outside as said members transmit the forces to the s in at many points, thus reducing the bending moments. Flush plate girders stressed over their whole length by outside forces are, for instance, hull side walls and bulkhead bottom parts carrying the water pressures.

In a similar way the disposition of the cross members at close intervals is particularly advantageous with curved girders, as the forces to be transmitted from the girder to the vertical plate is transmitted to the latter at many points.

The invention can be equally applied to curved girders, such as coverings of fuselages, floats, wings or the like. The following has to be considered with regard to the intervals at which the force distributing members and/or bulkheads should be arranged on the curved surface.

If a section is made at right an les to the skin surface and in the direction 0 the folds produced by tension stress, a curved plane will be the result. By the tension stress the plate is stretched, so that the terminal points of the section plane, lying on the bulkheads, increase their reciprocal distance. Apart from this stretching the skin is elongated, as all elastic bodies. When the deformation due to the presence of the subject matter of the invention does not very substantially exceed that of a body with covering plate of shearing resistance, it is necessary, that the stretching be small in proportion to the elongation,'as otherwise the body would be too soft and of insuflicient resistance against vibrations.

It is recognized, that with the cross force transmitting members arran ed at not too small intervals, the amount o the stretching is relatively small, being, with the elasticity of the used metal (duralumin, iron etc.) about 1/2 of the elastic elongation, if the ratio of the cross member spacing to the diameter of curzved girder to be re-inforced is about 1 3 to 1:

In order to have the usual longitudinally running girders vertical to the plane of the late wall, it is desirable to arrange, in adition to the relatively weak bulkheads required for supporting the tension stressed skin, specially re-inforced or frame-work bulkheads at somewhat larger intervals.

It is also possible to so support the tension plate, that bull'heads arranged at somewhat greater intervals and used, as above mentioned, for the support of the girders, are connected by girder sections arranged longitudinally and at narrow reciprocal distances. This formof support, however, results in the use of more building material, as compared with the bulkheads arranged transversely to the plate curvature, as these latter are only stressed against pressure, whereas the former have to transmit the bending forces acting in the curved skin.

The accompanying drawings show, by way of example, several embodiments of the said invention.

Figs. 1 to 3 represent a boat-shaped fuselage of a seaplane, in side elevation, in horizontal section on line II-II and cross section on line III-III of Fig. 1.

Figs. 4 and 5 are a wing portion in plan view with removed top skin and in section on line V-V of Fig. 4.

Figs. 6 and 7 are bulkheads.

Fig. 8 shows a section on line VIII-VIII of Fig. 6.

Figs. 9 to 11 represent the wall of a hollow body to be used as fuselage, float or the like, of substantially round section, wherein Fig. 9 is a cross section, Fig. 10 a section on line X, Fig. 11 a section on line XIXI of In Figs. 1 to 3 I have shown my invention as embodied in the main body or float a of a flying boat. The boat structure includes the upper angle girders b, the chime girders 0 and the keel girder d, which are interconnected by a thin plate covering skin e. 011 the inner side of the skin are arranged the cross force transmitting members, inserted between the girders at somewhat small reciprocal intervals, forming bulkheads f of Which some serve at the same time as watertight bulkheads 7. The skin of the boat walls, which are smooth and without corrugations forms diagonal folds when stressed, which folds, according to the particular prevailing conditions of the structure, are inclined towards the girders b, 0 by 35 to 45, one of these folds being indicated at 9. These diagonal folds are continuous and uninterrupted from girder to girder and each of them crosses several of the cross bulkheads f, as can be seen in Fig. 1. Owing to the close succession of the bulkheads the water pressure acting on every chime girder is transmitted to the skin in many points, so that the resulting bending forces in the girders are but small.

Figs. 4 and 5 show the invention applied to an aircraft wing. The central portion of said wing consists of two longitudinal web girders 2', interconnected by means of transverse connecting t-ies 9' arranged at somewhat larger intervals. Web girder and cross connections are covered by the outer skin attached to their girder members. The skin parallel to the latter being rigidly connected with the web girders c. Thedotted line 9 indicated in Fig. 4 represents another tension .dia onal or fold, passing over several of the pus bars 12.. It is not essential for the plate wall girder the members n be arranged on either the inside or outside of the skin. For

reasons of worksho manufacture, however,

these members are disposed, in ontradistinc-:

- straight girder members 0, p, the lower girder vals.

necting members a arranged at close interp being bent in the middle in order to obtain an inclined bottom surface. Both girders are again interconnected by means of a thin vertical plate 9 and a large number of transverse force transmitting members r the latter being arranged. on both sides of the plate and some of them being arranged and connected in pairs to opposite sides of the plate in the same plane.

The lower part of thebulkhead according to Fig. 7 is provided with partly straight and partly curved girder members 8, and the strai ht 'rders o, the central bulkhead portion r ered by the straight girder 0 and the straight parts of girder s forming a frame work girder, whilst the bulkhead end portions above the curvatures are provided with vertical plating of thin walls and cross connecting members 1* arranged at close inter- The curved bending girder according to Figs. 9 to 11 forms a hollow body, whose skin consists of platin with thin walls t, rein-- forced on its insi e by means of curved convals, said .members bein crossed by longitudinal girders 'v, 'v," orming the gir er members of the supportin system. Several connecting members, indicated b a, particularly are rovided to serve oi. the reinforcement o the girders against axial compression, being, for'this reason, of special structural resistance.

After havingthusdescribed thenature of my said invention and the .manner after which same has to be performed, I declare that what I claim is: j 1. A flush late wall girder as a structural member of air craft or the like, comprising girder membersimmembers disposed between the girder mem rs and transverse thereto, said transverse members being fixedly secured to the girder members and spaced apart so that their distances from each other may vary between limits expressed by one-eighth to three-quarters of the girder depth, and a substantially mooth 'web plate so thin that it is stressed by-transverse forces acting on smoothed out and disappear when the stress is removed.

2. A sheet wall girder according to claim 1 wherein the comression members are fixedly secured to the glrder members'in accordance with the stresses to which they are subjected, while at the same time they are lightly attachedto the web plate.-

3. A sheet wall girder according to claim 1 wherein the compression members are arranged on opposite sides of the web directly face each other.

4. A sheet wall girder according to claim 1 embodied as a structural, member of a seaplane, said seaplane structural member bemg arranged so that its bottom flange will be subjected to stress by the pressure of the water.

5. A substantially smooth metallic wall element for a hollow box-shaped body constituting a plate wall girder comprising girder members, cross ties and a web plate,

plate and I said cross ties being strongly secured to the girder members and more lightly secured to the web plate, the space between each two cross ties being within limits expressed by one-eighth to three-quarters of the girder depthiland the web plate being of such thin- I ness t at when stressed by transverse forces produced under normal service conditions on the girder, said web plate constitutes a closed panel of tensile diagonals produced by folds 1n the smooth surface of the plate. 1

6. A sheet wall irder according to claim 1 characterized by the fact that at least one of the girder members is curved,-the com ression members interconnecting the two girder members being rigid and fixedly secured to the girder members and so arranged that when the girder is subjected to normal stress the force component following the curvature of the curved girder member will be transmitted to the web plate.

7. A hollow metallic angular unit especially adapted for aircraft construction, pomprised of a pair of longitudinal spars,cross ties connecting said spars and comparatively widely spaced; a .smooththinsheet metal covermg secured to the cross ties, and additional ties arranged at close intervals between the cross ties and extending transvers'el of the s ars and seciired thereto, the

space etween t e additional ties bein lim ited to. distances expressed by one-eig th to three-quarters of the girder depth, the whole constituting a plate wall girder of which the spars aregirder members and" the covering.

duced automatically by oblique foldings or creasings of the plate.

8. A hollow metal angular unit according i to claim 7 wherein a plurality of the cross ties form bulkheads, the compression elements being secured to the web plate.

9. An air-craft wing including a boxshaped part consisting of two longitudinal spars, interconnecting cross ties, and flush top and bottom covering skins constituting a plate wall girder with the web plate formed. by the covering skins, and the girder members by the longitudinal spars, said Web plate being secured to the cross ties, and compression members arranged betweenthe cross ties and transverse to the girder members, said compression members being secured to the girder members and having attachments to the web plate and being closely spaced within limits represented by one-eighth to three quarters of the girder depth, the plate being of such thinness that when stressed by ordinary forces produced under normal service conditions acting on the girder such plate will constitute a closed panel of tensile diagonals produced automatically by oblique foldings or creasings of the plate.

10. A curved plate wall girder for use in aircraft, comprised of girder members running substantially in the direction of the curvature axis, compression members arranged between the girder members' andsecured thereto at intervals which may vary from about one-third to one-seventh of the curvature radius of the girder, and a thin web plate to which the compression members are connected, said web plate being of such thin cross section that under stresses resulting from transverse forces set up under ordinary service conditions it will constitute a closed panel of tensile diagonal throwing oblique folds or creases.

11. A substantially round hollow unit of light metal for aircraft constructionconsisting of longitudinal spars running substantially in the direction of the curvature axis,

curved plates interconnecting said spars,

' each pair of adjacent spars comprising with their interconnected plates a curved plate wall girder comprising compression members disposed transversely to the spars and secured to the spars and to saidplates, the compression members being spaced apart at distances within limits expressed by onethird to one-seventh of the curvature radius,

a certain of the compression members consti- 

